As the fall approaches, the days get shorter and shorter. This is the time of the year where our free energy source, sunlight, becomes limited. Sunlight is essential to maintain the global temperature in the ranges appropriate for plant growth. In winter, plant production is challenging because temperature and solar radiation decline to their minimum values.
In addition, there are several cloudy days which further diminish photosynthesis. Nevertheless, greenhouses are designed to minimize the negative effects of those environmental constraints. As winter approaches, the need for heating increases. The energy consumed to heat a greenhouse can be as high as 80% of the total energy required to run a greenhouse business.